The present invention is in a method for the production of dental spare parts, such as tooth-crowns and bridges, by means of spark erosion In this method a positive wax model is first fabricated, is then embedded into a casting mold and the wax is removed. Two form electrodes are prepared and the spare part is fabricated by means of spark erosion taking off material from an erosion body.
Such a method is described in the Deutsche Zahnarztliche Z 41, 525-526 (1986) under the title "Production of Metal Jacket Crowns Out of Full Material by Means of Spark Erosion". Pursuant to this method wax models of crown- or filling material [inlay material]are fabricated. The wax model is coated above and below the crown equator by a galvanic method with a copper layer having a thickness of about 1 mm. and the two copper molds, which can be separated in the area of the equator are lined with a reinforcing backing or rear construction. By means of the two form electrodes a metal molded blank is successively treated erosively. The two metal electrodes penetrate correspondingly into the erosive abrasion and form the dental spare piece of it. The accuracy of the spare piece to be eroded can be varied, especially in the area of its surface, by means of a modification of the abrasion speed. The article mentions that the spark erosion of such a spare part requires about an hour. The erosion time can be reduced by using a pre-formed metal body, serving as erosion body.
DE-PS 33 20 902 discloses a method for the production of tooth spare parts, especially casting fillings, part crowns or full crowns in which there is a precise fitting between the tooth frustrum and a spare part to be superimposed thereon. For this purpose in a multi-step procedure, a positive model of the tooth-frustrum is produced and the surface of the pre-fabricated tooth-surrogate to be fitted onto the tooth frustrum is adapted by means of an erosion procedure. Only very thin layers are eroded onto the pre-fabricated tooth spare part in the area of the posterior contact surface to the tooth frustrum.
EP-A2-0 225 513 , to which U.S. Pat. No. 4,734,173 corresponds, describes a procedure and arrangement for the production of tooth spare parts. In that method, the tooth spare piece to be fabricated is produced directly by means of a spark erosion by means of two form electrodes, out of a full, not previously treated material. As discussed above, the erosive abrasion for the production of the tooth spare piece is very time-consuming.